Species of crustacean

The coconut crab ( Birgus latro ) is a species of terrestrial anchorite crab, besides known as the robber crab or palm thief. It is the largest terrestrial arthropod in the world, with a weight of up to 4.1 kg ( 9 pound ). It can grow to up to 1 molarity ( 3 foot 3 in ) in width from the tip off of one leg to the tap of another. It is found on islands across the indian Ocean, and parts of the Pacific Ocean as far east as the Gambier Islands and Pitcairn Islands, similar to the distribution of the coconut palm ; it has been extirpated from most areas with a meaning human population, including mainland Australia and Madagascar. Coconut crab besides live off the coast of Africa near Zanzibar. The coconut cancer is the entirely species of the genus Birgus, and is related to the early terrestrial anchorite crab of the genus Coenobita. It shows a number of adaptations to life sentence on land. Juvenile coconut crab use empty gastropod shells for protection like other hermit crabs, but the adults develop a hard exoskeleton on their abdomens and stop carrying a shell. Coconut crabs have organs known as branchiostegal lungs, which they use for breathing alternatively of their vestigial gills. After the juvenile stage, they will drown if immersed in water for excessively long. They have an acute accent sense of smell which they use to find electric potential food sources, and which has developed convergently with that of insects.

Adult coconut crabs feed chiefly on fleshy fruits, nuts, seeds, and the pith of fallen trees, but they will eat carrion and other organic matter opportunistically. Anything left unattended on the grind is a potential source of food, which they will investigate and may carry away – thereby getting the option name of “ robber crab. ” The species is popularly associated with the coconut palm, yet coconuts are not a meaning part of its diet. Although it lives in a burrow, the crab has been filmed climbing coconut and pandanus trees. No film shows a cancer selectively picking coconut fruit, though they might dislodge ripe fruit that otherwise would fall naturally. Climbing is an immediate escape route ( if besides far from the burrow ) to avoid predation by large sea birds ( when young ) or by humans, or cannibalism ( at any historic period ) by bigger, older crab. Mating occurs on dry land, but the females return to the edge of the sea to release their fertilized eggs, and then retreat back up the beach. The larva that hatch are planktonic for 3–4 weeks, before settling to the sea shock, entering a gastropod shell and returning to dry domain. sexual maturity is reached after about 5 years, and the total life may be over 60 years. In the 3–4 weeks that the larva stay at sea, their chances of reaching another suitable location is enhanced if a floating life documentation system avails itself to them. Examples of the systems that provide such opportunities include floating logs and rafts of marine or mundane vegetation. similarly, floating coconuts can be a very significant separate of the crab ‘s dispersion options. [ 4 ] Fossils of this crab date back to the Miocene. [ 5 ]

taxonomy [edit ]

The coconut crab has been known to western scientists since the voyages of Francis Drake around 1580 [ 6 ] and William Dampier around 1688. [ 7 ] Based on an account by Georg Eberhard Rumphius ( 1705 ), who had called the animal “ Cancer crumenatus “, Carl Linnaeus ( 1767 ) named the species Cancer latro, [ 8 ] from the Latin latro, meaning “ robber ”. The genus Birgus was erected in 1816 by William Elford Leach, containing only Linnaeus ‘ Cancer latro, which was therefore renamed Birgus latro. [ 3 ] Birgus is classified in the family Coenobitidae, aboard one other genus, Coenobita, which contains the tellurian anchorite crab. [ 3 ] [ 9 ] coarse names for the species include coconut crab louse, robber crab, and palm thief, [ 1 ] which mirrors the animal ‘s diagnose in other european languages ( e.g. german : Palmendieb ). [ 10 ] In Japan ( where the species lives on some of the country ‘s south wind island chains ), the species is typically referred to as Yashigani ( ヤシガニ ), meaning ‘palm gripe ‘. [ 11 ]

description [edit ]

B. latro is the largest tellurian arthropod, and indeed mundane invertebrate, in the world ; [ 12 ] [ 13 ] reports about its size vary, but most sources give a torso length up to 40 centimeter ( 16 in ), [ 14 ] a weight up to 4.1 kg ( 9 pound ), and a leg span more than 0.91 m ( 3 foot ), [ 15 ] with males generally being larger than females. [ 16 ] The carapace may reach a distance of 78 millimeter ( 3+1⁄16 in ), and a width up to 200 millimeter ( 8 in ). [ 13 ] The body of the coconut crab is, like that of all decapods, divided into a presence section ( cephalothorax ), which has 10 leg, and an abdominal cavity. The front-most match of peg has bombastic chela ( claw ), with the exit being larger than the right. [ 17 ] The future two pairs, as with other hermit crabs, are big, brawny walking legs with luff tips, which allow coconut crab to climb vertical or overhang surfaces. [ 18 ] The fourth copulate of leg is smaller with pincer -like claw at the end, allowing unseasoned coconut gripe to grip the at heart of a beat or coconut chaff to carry for protection ; adults use this match for walking and climbing. The death pair of leg is very small and is used by females to tend their eggs, and by the males in mating. [ 17 ] This stopping point pair of legs is normally held inside the carapace, in the cavity containing the breathe organs. Some remainder in color occur between the animals found on different islands, ranging from orange-red to purplish gloomy ; [ 19 ] in most regions, blue is the prevailing color, but in some places, including the Seychelles, most individuals are crimson. [ 17 ] Although B. latro is a deduce type of anchorite crab, only the juveniles use salvaged escargot shells to protect their soft abdomens, and adolescents sometimes use break coconut shells for that purpose. Unlike other anchorite crabs, the adult coconut crabs do not carry shells, but alternatively harden their abdominal terga by depositing chitin and chalk. not being constrained by the physical confines of survive in a shell allows this species to grow much larger than early anchorite crabs in the kin Coenobitidae. [ 20 ] Like most dependable crab, B. latro bends its tail underneath its body for protection. [ 17 ] The harden abdomen protects the coconut crab and reduces water loss on land, but must be moulted sporadically. Adults moult annually, and dig a burrow up to 1 thousand ( 3 foot 3 in ) long in which to hide while vulnerable. [ 18 ] It remains in the burrow for 3–16 weeks, depending on the size of the animal. [ 18 ] Depending on the animal ‘s size, 1–3 weeks are needed for the exoskeleton to harden after moulting, during which time the animal ‘s body is soft and vulnerable, and it stays hidden for protective covering. [ 21 ]

respiration [edit ]

Dictionnaire d’Histoire Naturelle of 1849 print of a coconut crab from theof 1849 Except as larva, coconut crabs can not swim, and they drown if left in body of water for more than an hour. [ 17 ] They use a special harmonium called a branchiostegal lung to breathe. This organ can be interpreted as a developmental stage between gills and lungs, and is one of the most significant adaptations of the coconut crab to its habitat. [ 22 ] The branchiostegal lung contains a weave similar to that found in gills, but suited to the preoccupation of oxygen from air out, preferably than water. This organ is expanded laterally and is evaginated to increase the surface area ; [ 18 ] located in the cephalothorax, it is optimally placed to reduce both the blood/gas dispersion distance and the restitution distance of oxygenate blood to the pericardium. [ 23 ] Coconut crabs use their backmost, smallest pair of legs to clean these breathing organs and to moisten them with water system. The organs require water to properly function, and the coconut crab louse provides this by stroking its wet stage over the spongy tissues nearby. Coconut crab may drink water from little puddles by transferring it from their chelipeds to their maxillipeds. [ 24 ] In addition to the branchiostegal lung, the coconut crab has an extra fundamental put of gills. Although these gills are comparable in numeral to aquatic species from the families Paguridae and Diogenidae, they are reduced in size and have relatively less surface area. [ 23 ]

feel of smack [edit ]

The coconut crab louse has a well-developed sense of smell, which it uses to locate its food. [ 25 ] The process of smelling works identical differently depending on whether the smell molecules are hydrophilic molecules in water or hydrophobic molecules in breeze. Crabs that live in water have specialized organs called aesthetascs on their antenna to determine both the density and the direction of a odorize. Coconut crab louse live on the land, so the aesthetascs on their antenna are shorter and blunter than those of other crabs and are more exchangeable to those of insects. [ 25 ] While insects and the coconut crab originate from different paths, the same need to track smells in the atmosphere led to the growth of signally like organs. Coconut crabs flick their antenna as insects do to enhance their reception. Their sense of smell can detect interest odors over large distances. The smells of rotting kernel, banana, and coconuts, all potential food sources, catch their attention particularly. [ 26 ] The olfactory system in the coconut gripe ‘s brain is well-developed compared to early areas of the brain. [ 27 ]

Lifecycle [edit ]

Coconut crab match frequently and cursorily on dry farming in the menstruation from May to September, particularly between early June and former August. [ 28 ] Males have spermatophores and deposit a mass of spermatophores on the abdomens of the females ; [ 29 ] the oviducts opens at the basis of the third base pereiopods, and fertilization is thought to occur on the external surface of the abdomen, as the egg pass through the spermatophore multitude. [ 30 ] The bulge of testis occurs on land in crevices or burrows near the shore. [ 31 ] The female lays her eggs curtly after mating and glues them to the bottom of her abdomen, carrying the fertilised eggs underneath her body for a few months. At the time of hatch, the female coconut gripe migrates to the seashore and releases the larva into the ocean. [ 30 ] The coconut crab takes a large hazard while laying the eggs because coconut crabs ca n’t swim. If a coconut cancer falls into the water or gets sweep away, its weight makes it unmanageable, or impossible, for it to swim back to dry land. [ 32 ] The testis laying normally takes rate on rough shores at dusk, particularly when this coincides with high tide. [ 33 ] The evacuate testis cases remain on the female ‘s body after the larva have been released, and the female eats the egg cases within a few days. [ 33 ] The larva float in the oceanic partition of the ocean with other plankton for 3–4 weeks, [ 13 ] during which a large count of them are eaten by predators. The larva passing through three to five zoea stages before moulting into the postlarval glaucothoe stage ; this process takes from 25 to 33 days. [ 34 ] Upon reaching the glaucothoe stage of development, they settle to the bottom, find and wear a appropriately sized gastropod shell, and migrate to the shoreline with early tellurian anchorite crab. [ 35 ] At that time, they sometimes visit dry land. Afterwards, they leave the ocean permanently and lose the ability to breathe in water. As with all hermit crabs, they change their shells as they grow. Young coconut crab that can not find a seashell of the correct size often use break coconut pieces. When they outgrow their shells, they develop a tempered abdomen. The coconut crab reaches sexual maturity around 5 years after hatching. [ 30 ] They reach their utmost size alone after 40–60 years. [ 18 ] It grows signally slowly, taking possibly 120 years to reach full moon size, as posited by ecologist Michelle Drew of the Max Planck Institute. [ 36 ]

distribution [edit ]

Coconut crabs live in the amerind Ocean and the cardinal Pacific Ocean, with a distribution that closely matches that of the coconut handle. [ 37 ] The western terminus ad quem of the scope of B. latro is Zanzibar, off the coast of Tanzania, [ 9 ] while the tropics of Cancer and Capricorn mark the northerly and southerly limits, respectively, with identical few population in the subtropics, such as the Ryukyu Islands. [ 13 ] Some evidence indicates the coconut cancer once lived on the mainland of Australia, Madagascar, Rodrigues, Easter Island, Tokelau, the Marquesas islands, and possibly India, but is immediately locally extinct in those areas. [ 13 ] [ 1 ] As they can not swim as adults, coconut crab must have colonised the islands as planktonic larva. [ 38 ]

Christmas Island in the amerind Ocean has the largest and densest population of coconut pediculosis pubis in the world, [ 25 ] although it is outnumbered there by more than 50 times by the Christmas Island red cancer ( Gecarcoidea natalis ). [ 39 ] other indian Ocean populations exist on the Seychelles, including Aldabra and Cosmoledo, [ 40 ] but the coconut crab is extinct on the central islands. [ 41 ] Coconut crabs occur on respective of the Andaman and Nicobar Islands in the Bay of Bengal. They occur on most of the islands, and the northern atolls, of the Chagos Archipelago. [ 42 ] In the Pacific, the coconut cancer ‘s range became known gradually. Charles Darwin believed it was only found on “ a single coral island north of the Society group “. [ 43 ] The coconut crab louse is far more far-flung, though it is not abundant on every Pacific island it inhabits. [ 43 ] Large populations exist on the Cook Islands, specially Pukapuka, Suwarrow, Mangaia, Takutea, Mauke, Atiu, and Palmerston Island. These are close up to the easterly limit of its range, as are the Line Islands of Kiribati, where the coconut crab is particularly frequent on Teraina ( Washington Island ), with its abundant coconut palm forest. [ 43 ] The Gambier Islands mark the species ‘ easterly limit. [ 9 ]

ecology [edit ]

diet [edit ]

A coconut cancer atop a coconut The diet of coconut crab consists chiefly of fleshy fruits ( particularly Ochrosia ackeringae, Arenga listeri, Pandanus elatus, P. christmatensis ) ; nuts ( Aleurites moluccanus ), drupes ( Cocos nucifera ) and seeds ( Annona reticulata ) ; [ 44 ] and the kernel of fallen trees. [ 45 ] however, as they are omnivores, they will consume other organic materials such as tortoise hatchlings and dead animals. [ 18 ] [ 46 ] They have been observed to prey upon crabs such as Gecarcoidea natalis and Discoplax hirtipes, equally well as scavenge on the carcasses of early coconut crabs. [ 44 ] During a chase experiment, one coconut cancer was observed kill and eating a polynesian rat ( Rattus exulans ). [ 47 ] In 2016, a large coconut crab was observed climbing a corner to disable and consume a red-footed dumbbell on the Chagos Archipelago. [ 48 ] [ 49 ] The coconut crab can take a coconut from the land and cut it to a husk crackpot, take it with its claw, climb up a tree 10 molarity ( 33 foot ) high and drop the husk crackpot, to access the coconut flesh inside. [ 50 ] They frequently descend from the trees by falling, and can survive a fall of at least 4.5 thousand ( 15 foot ) safe and sound. [ 51 ] Coconut crab ignore holes into coconuts with their firm claws and eat the contents, although it can take respective days before the coconut is opened. [ 45 ] Thomas Hale Streets discussed the behavior in 1877, doubting that the animal would climb trees to get at the coconuts. [ 43 ] In the 1980s, Holger Rumpf was able to confirm Streets ‘ composition, observing and studying how they open coconuts in the wild. [ 45 ] The animal has developed a extra proficiency to do sol ; if the coconut is still covered with husk, it will use its claw to rip off strips, constantly starting from the english with the three germination pores, the group of three small circles found on the outdoor of the coconut. Once the pores are visible, the coconut crab bangs its pincers on one of them until it breaks. Afterwards, it turns about and uses the smaller pincers on its early leg to pull out the white human body of the coconut. Using their potent claws, larger individuals can even break the heavily coconut into smaller pieces for easier consumption. [ 52 ]

habitat [edit ]

Coconut crabs vary in size and discolor. Coconut crabs are considered one of the most terrestrial-adapted of the decapods, [ 53 ] with most aspects of its life oriented to, and centered around such an being ; they will actually drown in sea water in less than a day. [ 24 ] Coconut crab louse live alone in burrows and rock crevices, depending on the local terrain. They dig their own burrows in sandpaper or loose soil. During the day, the animal stays hidden to reduce water loss from heat. The coconut crab ‘ burrows contain very finely so far hard fibres of the coconut husk which the animal uses as bedclothes. [ 43 ] While resting in its burrow, the coconut gripe closes the entrances with one of its claws to create the damp microclimate within the burrow, which is necessity for the operation of its breathing organs. In areas with a bombastic coconut cancer population, some may come out during the day, possibly to gain an advantage in the search for food. other times, they emerge if it is damp or rain, since these conditions allow them to breathe more easily. They live about entirely on domain, returning to the sea only to release their eggs ; on Christmas Island, for exemplify, B. latro is abundant 6 kilometer ( 3+1⁄2 nautical mile ) from the ocean. [ 54 ]

relationship with humans [edit ]

Adult coconut crabs have no known predators apart from other coconut crabs and humans. Its large size and the quality of its kernel means that the coconut cancer is extensively hunted and is very rare on islands with a human population. [ 55 ] The coconut cancer is eaten as a delicacy – and regarded as an aphrodisiac – on assorted islands, and intensive hunt has threatened the species ‘ survival in some areas. [ 19 ] While the coconut crab itself is not innately poisonous, it may become so depending on its diet, and cases of coconut crab louse poisoning have occurred. [ 55 ] [ 56 ] For case, consumption of the ocean mango, Cerbera manghas, by the coconut crab may make the coconut crab toxic due to the bearing of cardiac cardenolides. [ 57 ] The pincers of the coconut crab are powerful adequate to cause obtrusive pain to a human ; furthermore, the coconut crab louse often keeps its apply for cover periods of time. Thomas Hale Streets reports a flim-flam used by Micronesians of the Line Islands to get a coconut crab to loosen its grip : “ It may be interesting to know that in such a dilemma a gentle titillation of the under soft parts of the body with any light material will cause the crab to loosen its cargo area. ” [ 43 ] In the Cook Islands, the coconut crab is known as unga or kaveu, and in the Mariana Islands it is called ayuyu, and is sometimes associated with taotaomo’na because of the traditional impression that ancestral spirits can return in the form of animals such as the coconut crab louse. [ 58 ]

conservation [edit ]

Coconut gripe populations in respective areas have declined or become locally extinct due to both habitat loss and human depredation. [ 59 ] [ 60 ] In 1981, it was listed on the IUCN Red List as a vulnerable species, but a miss of biological data caused its judgment to be amended to “ data insufficient “ in 1996. [ 13 ] In 2018, IUCN updated its appraisal to “ vulnerable ”. [ 1 ] Conservation management strategies have been put in place in some regions, such as minimum legal size limit restrictions in Guam and Vanuatu, and a bachelor of arts in nursing on the capture of egg-bearing females in Guam and the Federated States of Micronesia. [ 61 ] In the Northern Mariana Islands, hunting of non-egg-bearing adults above a carapace length of 76 millimeter ( 3 in ) may take place in September, October, and November, and merely under license. The pocket restrict is five coconut pediculosis pubis on any given day, and 15 across the solid season. [ 62 ] In Tuvalu, coconut crabs live on the motu ( islets ) in the Funafuti Conservation Area, a marine conservation area covering 33 km2 ( 12.74 mi2mi ) of reef, lagoon and motu on the western side of Funafuti atoll. [ 63 ]

References [edit ]

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